Prognostic Significance of Real-Time RT-PCR Detection of Disseminated Tumour Cells in Bone Marrow and Circulating Tumour Cells in Patients with Breast Cancer.

Abstract

Abstract Background: Despite optimal staging and treatment, up to 40% of stage I and II breast cancer (BC) patients will develop recurrent disease over time. These patients are believed to have disseminated tumour cells (DTC) at the time of diagnosis. Detection of minimal disease in bone marrow (BM) has been suggested to be a more direct approach to select metastasis-prone patients among this 'good prognosis group'. Peripheral blood (PB) sampling however is more convenient. The aim of this study was to evaluate whether the detection of DTC in either PB or BM predicts overall survival (OS). The initial analysis was published with a mean follow up time of 786 days (Benoy et al., BrJC 2006). We now report on these data after a mean follow up of nearly 5 years.Material and methods: PB and BM samples were collected from 148 patients with primary (M0, n=116) and metastatic (M+, n=32) BC before the initiation of any local or systemic treatment. PB of healthy volunteers and BM of patients with a nonmalignant breast lesion or a haematological malignancy served as control group. DTC were detected by measuring relative gene expression (RGE) for cytokeratin 19 (CK19) and mammaglobin (MAM), using a quantitative RT-PCR detection method. The 95 percentile of the RGE for CK19 and MAM of the control group was used as cutoff to determine elevation in BC patients. Kaplan-Meier analysis was used to predict OS.Results: Mean follow up time was 1518 days (+/- 719). Elevated CK19 expression was detected in 42 (28%) BM samples and in 22 (15%) PB samples. MAM expression was elevated in 20% (both PB and BM) of the patients with BC. There was a 68% (CK19) and 75% (MAM) concordance between PB and BM samples when classifying the results as either positive or negative. Patients with an elevated CK19 or MAM expression in BM had a worse OS than patients without elevated expression levels (p=0.002 (CK19) and p=0.001 (MAM)). For PB, no statistical significant difference in OS was observed between patients with or without elevated CK19 (p=0.227), but a strong trend for predicting OS was observed according to MAM status (p=0.054). Separate analyses of M0 and M+ patients revealed only a marked difference in OS according to BM CK19 in the M+ patient group. In M0 patients disease free survival (DFS) was not significantly predicted by CK19 and/or MAM status in BM alone (p=0.173 (CK19), p=0.219 (MAM)), but the presence of the double positive phenotype showed a trend for predicting DFS (p=0.059).Conclusions: DTC measured as elevated CK19 or MAM mRNA expression, could be detected in both PB and BM of patients with BC. Only the presence of DTC in BM was highly predictive for OS. However, with longer follow up differences in OS between patients with or without elevated CK19 and particularly MAM expression in PB also tend to become more significant. Furthermore, on the long term, double positivity for CK19/MAM in BM seems to predict DFS in patients with localized BC. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 3019.